Testing is an essential part of software development, but it can be a tricky and time-consuming process. The popular testing-library package is a widely used tool that helps developers write reliable and maintainable frontend tests based on a behavior driven approach, but many users are not fully aware of how it works or why it works the way it does. In this talk, I, as one of the maintainers of the package, give an in-depth look into the testing-library ecosystem, including its structure and foundations. I explain how we built a solution that can be used in every framework, and how you can use it in both Node and browser environments. You will learn how testing-library is designed to encourage good testing practices and how it can help you write more maintainable tests.